A self-aligning roller bearing with a cage according to the present invention is used, e.g., to support a rotating shaft inside a housing while assembled to various types of machinery.
For example, to rotatably support a heavy shaft inside a housing, a self-aligning roller bearing such as disclosed in, e.g., Unexamined Japanese Patent Publication No. Hei. 5-157116 has been used conventionally. This self-aligning roller bearing with a cage is, as shown in FIG. 11, formed by arranging a plurality of barrel-shaped rollers 3, 3 so as to be rollable between an outer race 1 and an inner race 2, both races being concentrically assembled. Cages 4, 4 prevent the plurality of barrel-shaped rollers 3, 3 from being separated from each other. The cages 4, 4 are so-called "pressed cages" formed by press-molding a metal plate.
In the inner circumferential surface of the outer race 1 is formed an outer raceway 5 that is a spherically recessed surface having a single center. On both sides in the width direction of the outer circumferential surface of the inner race 2 (in the horizontal direction as viewed in FIG. 11) are formed a pair of inner raceways 6, 6, each of which confronts the outer raceway 5. The plurality of barrel-shaped rollers 3, 3 are so formed that each is symmetrical with respect to the largest diameter portion that is in the middle of the length thereof and are arranged in two rows between the outer raceway 5 and the pair of inner raceways 6, 6 so as to be rollable therebetween.
As shown in FIGS. 11 and 12, each of the cages 4, 4 has a conically cylindrical main portion 7 and an outward flange portion 8 extending outwardly in the radial direction from the large-diameter side edge portion of the main portion 7, and an inward flange portion 9 extending inwardly in the radial direction from the small-diameter side edge portion thereof. The main portion 7 has a plurality of pockets 10, 10. Each pocket 10 retains a single barrel-shaped roller 3 so as to be rollable therein.
The outer circumferential edges of the outer flange portions 8, 8 of the pair of cages 4, 4 are guided by a guide ring 11 so as to be in slidable contact with the inner circumferential surface of the guide ring 11. This guide ring 11 is disposed so as to be rotatable between the two rows into which the plurality of barrel-shaped rollers 3, 3 are arranged. Further, both side surfaces of the guide ring 11 guide the barrel-shaped rollers 3, 3 by the side surfaces thereof which approach ends of two respective barrel-shaped rollers 3, 3 to prevent the axes of rotation of the barrel-shaped rollers 3, 3 from being skewed from the regular positions.
To support, e.g., a rotating shaft inside a housing with the thus constructed self-aligning roller bearing with the cage, the outer race 1 is firmly fitted into the housing from inside and the inner race 2 is firmly fitted over the rotating shaft from outside. If the inner race 2 is rotated together with the rotating shaft, the plurality of barrel-shaped rollers 3, 3 are rolled to allow the inner race 2 to be rotated. If the axial center of the housing is not aligned with that of the rotating shaft, then it is the inner race 2 that adjusts the alignment within the outer race 1 (the center axis of the inner race 2 is caused to be inclined with respect to that of the outer race 1) to correct such misalignment. In this case, since the outer raceway 5 is formed so as to be a single spherical surface, the rolling of the plurality of barrel-shaped rollers 3, 3 can be effected smoothly even after the misalignment has been rectified.
As shown in FIG. 13, a self-aligning roller bearing using cages 4a, 4a that do not have the outward flange portions 8, 8 (see FIGS. 11 and 12) and inner circumferential surfaces on ends of these cages 4a, 4a which oppose the outer circumferential edges of a guide ring 11a is also available. Like the above-mentioned structure, this structure shown in FIG. 13 is also designed to guide the barrel-shaped rollers 3, 3 with both side surfaces of the guide ring 11a nearing the ends of the barrel-shaped rollers 3, 3 so that skewing of the barrel-shaped rollers is prevented.
However, in the thus constructed and operating conventional self-aligning roller bearing with the cage, there are the following problems to be overcome.
That is, when a large axial load is applied to the self-aligning roller bearing with the cage, only the rolling surfaces of the barrel-shaped rollers 3 in one row out of the barrel-shaped rollers 3, 3 in two rows are abutted against the outer raceway 5 and the inner raceway 6 to strongly support the load. The pressure at which the rolling surfaces of the barrel-shaped rollers in the other row are abutted against both raceways 5, 6 is reduced almost to zero, so that the barrel-shaped rollers 3 in the other row can move in the axial direction. As a result, each of the guide rings 11, 11a is displaceable toward the barrel-shaped rollers 3 in the other row. When each of the guide rings 11, 11a is displaced, the distance between the ends of the barrel-shaped rollers 3 in the one row and the side surface of each of the guide ring 11, 11a becomes so large that the barrel-shaped rollers 3 in the one row tend to skew.
For example, in the self-aligning roller bearings with the cages as shown in FIGS. 11, 13, when an axial load is applied to the outer race 1 in the left direction or to the inner race 2 in the right direction, the guide rings 11, 11a are displaceable in the left direction in both figures. The barrel-shaped rollers 3 on the right side row are easily skewed while supporting the axial load.
When the barrel-shaped rollers 3 supporting the load have skewed, the frictional force acting between the rolling surfaces of the barrel-shaped rollers 3 and the inner and outer raceways 5, 6 is excessively large, so that there is an increase in the torque for rotating the self-aligning roller bearing with the cage. Besides, if the frictional force is extremely large, the rollers seize up so that the self-aligning roller bearing causes breakdown. On the other hand, the skewing of a barrel-shaped roller 3 that is substantially free from thrust load (the barrel-shaped roller 3 on the left side in both figures) is not objectionable.
Further, as shown in FIG. 13, in the case of guiding the guide ring 11a into the inner race 2, rolling slippage in which the inner circumferential edge of the guide ring 11a slidably contacts the outer circumferential surface of the inner race 2 in the direction of rolling, occurs and such rolling slippage occurs also between the guide ring 11a and the barrel-shaped rollers 3. The frictional heat derived from the rolling slippage increases the temperature within the self-aligning roller bearing, which in turn deteriorates the performance of the self-aligning roller bearing.